Friday 8 June 2012 15.11 EDT
First published on Friday 8 June 2012 15.11 EDT

The Metropolitan police are urging scores of women from north London who have been raped or sexually abused to come forward if they feel their cases were not taken seriously, after arresting another detective in its flagship sex crime unit Sapphire for allegedly falsifying documents.

The arrest stems from one of three investigations into failings in the unit, which could have left rapists at large.

The detective constable – who has not been named – was arrested on Friday on suspicion of perverting the course of justice. Colleagues raised allegations that he had altered crime documents by inserting statements from the Crown Prosecution Service and senior officers to indicate that no charges were to be brought in rape and sexual abuse cases when no such decision had been made.

The officer was involved in 63 cases – 26 of which are continuing, and 37 in which he claimed the inquiry was completed. Each case is being reviewed and at least two women have already been told by detectives that issues have come to light which mean the original decision has now been changed, and the investigation is taking a different course.

The arrest comes less than a week after another former Sapphire officer, Ryan Coleman-Farrow, 30, was charged with 13 counts of misconduct in a public office after concerns were raised about the way he conducted crime investigations and allegations that he had also falsified statements and reports. Coleman-Farrow was dismissed from the Met in April 2011. It is alleged that he wrote letters to sexual assault and rape victims telling them their investigations had been shelved, when no such decision has been made.

The Independent Police Complaints Commission – which was involved in investigating both cases – is also carrying out a third investigation into the working practices of the Sapphire unit based in Southwark, south London between July 2008 and September 2009 following repeated concerns about the way it has been functioning.

The focus on Sapphire, the Met's sex crimes department, comes after senior officers claimed less than three years ago that it had been reformed following a series of scandals in which two serial rapists were left at large to rape and abuse hundreds of women.

Scotland Yard at the time apologised for letting down victims after the failures in Sapphire, which were exposed by the cases of John Worboys, a black-cab driver and one of Britain's most prolific serial rapists, and Kirk Reid, a south London chef who raped and sexually assaulted more than 71 women over eight years.

Both men had been allowed to continue abusing women, despite repeated complaints to police by their victims, who in the case of Worboys were simply not believed by investigating detectives.

Reid, who was investigated by officers from Sapphire in Southwark, had been identified as a suspect for a series of sex attacks in 2004 and crossed the police radar at least 12 times, but no one pursued inquiries into him.

Scotland Yard acknowledged in the aftermath of the Reid and Worboys cases it was facing a "Macpherson moment" over its rape and sex crime investigations and said all the Sapphire teams would be taken under the control of the Yard centrally to tighten supervision and remove officers who were not up to the job.

But less than three years after the creation of the new centralised rape invesigation command there is renewed focus on how professionally rape and sex crime investigations are being carried out.

The latest arrest and some of the Coleman-Farrow charges concern cases that were run under the command of the new "reformed" centralised Sapphire unit.

A spokesman for Women against Rape, said Friday's revelations did nothing to improve public confidence in the investigation of rape and sexual abuse.

"Whether they are lazy, biased or corrupt officers who break the law aiding and abetting rapists should not only be sacked but prosecuted," said Lisa Longstaff.

"Women come to us asking just who they can go to? They do not trust the police and what we are hearing now will do nothing to improve that situation."

The IPCC said the detective arrested on Friday was not connected with the case of Coleman-Farrow but it is understood the allegations against both officers are similar – in that they falsifed records to make it appear that no charges should be laid against men accused of rape and sexual abuse.

Scotland Yard said Friday's arrest was made at an address in east London, and the detective constable concerned worked at the Sapphire unit covering Camden and Islington. It appealed for women from that area to contact them if they had concerns over the way their investigations were handled.

Officers from the Met's directorate of professional standards were questioning the detective on Fridaywhile searches were carried out at two premises linked to him. The investigation into the officer began last month.

"It was brought to the attention of the senior management of Sapphire that there may be inaccuracies in some of his crime reports," a spokesman said.

"The officer was suspended from duty on Friday 18 May, and due to recent significant developments in the investigation a decision was taken to arrest the officer."

The IPCC, who are running an independent investigation into the allegations were informed of the arrest.

"We want victims to have the confidence that we are here for them, will believe them and will conduct our investigations professionally," the Yard said.

"Victims must be at the heart of every rape investigation, knowing that lines of inquiry have been exhausted in an attempt to bring offenders to justice.

"Any suggestion that an investigation is not up to the high standard expected will be fully investigated and any officers involved in potential failings dealt with robustly."

Coleman-Farrow is due to appear at Westminster Magistrates court on 20 June.